A greener approach to synthesize magnetically separable and photocatalytic recyclable g-C3N4-Fe3O4 nanomaterial for removing toxic organic dyes from water

A greener and eco-friendly approach was developed to prepare magnetic g-C3N4-Fe3O4 nanocomposite adsorbent. Here, first g-C3N4 was prepared from melamine by using simple thermal treatment method. Then magnetic Fe3O4 nanoparticles were introduced on 2D surface of g-C3N4 using guava leaf extract. The formation, functionality, morphologies, surface area, magnetic power and bonding of the prepared material were analysed by XRD, FTIR, FESEM, TEM, BET, VSM and XPS analytical techniques. The formation of Fe3O4 phase on g-C3N4 surface was confirmed by XRD analysis. TEM images confirmed the formation of fine NPs on 2D g-C3N4 sheet. The surface area was found to be 92.32 m2/g with BJH average pore size distribution of 4 nm.The saturation magnetization value of g-C3N4-Fe3O4 was 15.12 emu/g. This shows superior magnetic property of the prepared material and thus can easily be separated from the treated water using external magnet. The prepared material was used for the removal of commonly used toxic Congo red (CR) and Methylene blue (MB) dyes from water using batch adsorption method. The adsorption of CR and MB on the surface of adsorbent was pH dependent. The maximum adsorption capacity of CR was found to be 194 mg/g at pH = 6 and MB was found to be 149 mg/g at pH = 8. The CR and MB adsorption process follows Pseudo- second-order kinetic and Langmuir isotherm models. The adsorbed CR and MB were recovered from the surface of adsorbent using chemical free photocatalytic irradiation process under visible light. The regenerated adsorbent was also reused for the further adsorption study and showed significant adsorption efficiency. This novel material can be considered as a promising adsorbent for CR and MB dyes with high adsorption efficiency, high stability, eco-friendly synthesis and easy to separate from the treated water with good reusability power.